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journal: make skipping of exhausted journal files effective again

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Commit 668c965af "journal: skipping of exhausted journal files is bad if
direction changed" fixed a correctness issue, but it also significantly
limited the cases where the optimization that skips exhausted journal
files could apply.
As a result, some journalctl queries are much slower in v219 than in v218.
(e.g. queries where a "--since" cutoff should have quickly eliminated
older journal files from consideration, but didn't.)

If already in the initial iteration find_location_with_matches() finds
no entry, the journal file's location is not updated. This is fine,
except that:
 - We must update at least f->last_direction. The optimization relies on
   it. Let's separate that from journal_file_save_location() and update
   it immediately after the direction checks.
 - The optimization was conditional on "f->current_offset > 0", but it
   would always be 0 in this scenario. This check is unnecessary for the
   optimization.
This commit is contained in:
Michal Schmidt 2015-02-24 19:45:17 +01:00
parent 3cabeab119
commit 950c07d421
3 changed files with 17 additions and 12 deletions
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3
src/journal/journal-file.c
View file

@ -2013,8 +2013,7 @@ void journal_file_reset_location(JournalFile *f) {
f->current_xor_hash = 0;
}
void journal_file_save_location(JournalFile *f, direction_t direction, Object *o, uint64_t offset) {
f->last_direction = direction;
void journal_file_save_location(JournalFile *f, Object *o, uint64_t offset) {
f->location_type = LOCATION_SEEK;
f->current_offset = offset;
f->current_seqnum = le64toh(o->entry.seqnum);

2
src/journal/journal-file.h
View file

@ -199,7 +199,7 @@ int journal_file_find_field_object(JournalFile *f, const void *field, uint64_t s
int journal_file_find_field_object_with_hash(JournalFile *f, const void *field, uint64_t size, uint64_t hash, Object **ret, uint64_t *offset);
void journal_file_reset_location(JournalFile *f);
void journal_file_save_location(JournalFile *f, direction_t direction, Object *o, uint64_t offset);
void journal_file_save_location(JournalFile *f, Object *o, uint64_t offset);
int journal_file_compare_locations(JournalFile *af, JournalFile *bf);
int journal_file_next_entry(JournalFile *f, uint64_t p, direction_t direction, Object **ret, uint64_t *offset);

24
src/journal/sd-journal.c
View file

@ -723,13 +723,17 @@ static int next_beyond_location(sd_journal *j, JournalFile *f, direction_t direc
assert(j);
assert(f);
if (f->last_direction == direction && f->current_offset > 0) {
/* If we hit EOF before, recheck if any new entries arrived. */
n_entries = le64toh(f->header->n_entries);
if (f->location_type == LOCATION_TAIL && n_entries == f->last_n_entries)
return 0;
f->last_n_entries = n_entries;
n_entries = le64toh(f->header->n_entries);
/* If we hit EOF before, we don't need to look into this file again
* unless direction changed or new entries appeared. */
if (f->last_direction == direction && f->location_type == LOCATION_TAIL &&
n_entries == f->last_n_entries)
return 0;
f->last_n_entries = n_entries;
if (f->last_direction == direction && f->current_offset > 0) {
/* LOCATION_SEEK here means we did the work in a previous
* iteration and the current location already points to a
* candidate entry. */
@ -738,14 +742,16 @@ static int next_beyond_location(sd_journal *j, JournalFile *f, direction_t direc
if (r <= 0)
return r;
journal_file_save_location(f, direction, c, cp);
journal_file_save_location(f, c, cp);
}
} else {
f->last_direction = direction;
r = find_location_with_matches(j, f, direction, &c, &cp);
if (r <= 0)
return r;
journal_file_save_location(f, direction, c, cp);
journal_file_save_location(f, c, cp);
}
/* OK, we found the spot, now let's advance until an entry
@ -773,7 +779,7 @@ static int next_beyond_location(sd_journal *j, JournalFile *f, direction_t direc
if (r <= 0)
return r;
journal_file_save_location(f, direction, c, cp);
journal_file_save_location(f, c, cp);
}
}